Stabilizing papermaking system cleaner operation

ABSTRACT

CLEANING EFFICIENCY IN PAPERMAKING SYSTEM CLEANERS IS ENHANCED BY FITTING ELUTRIATION UNITS ON THE REJECTS ENDS OF SYSTEM CLEANERS TO FURTHER DILUTE CLEANER REJECTS PORTIONS AND THEREBY RECOVER MORE USEABLE FIBER IN THE ACCEPTS PORTION, THE DILUTION BEING EFFECTED BY MEANS OF A STREAM OF ELUTRIATION WATER ADMITTED TO THE ELUTRIATION UNIT AT RELATIVELY LOW BUT CONSTANT PRESSURE, THE ACCEPTS AND REJECTS PORTIONS FROM SUCH CLEANERS BEING DISCHARGED FREELY INTO SPACES OF ZONES OF VACUUM OF SUBSTANTIALLY THE SAME CONDITION OF VACUUM PROVIDED BY AN UNOBSTRUCTED LIQUID-FREE CORE INTERCONNECTING SUCH SPACES.

March 13, 1973 R. G. KAISER 3,

STABILIZING *PAPERMAKING SYSTEM CLEANER OPERATION Filed Jan. 18, 1971 4 Sheets-Sheet 1 March 13, 1973 R. G. KAISER Y 3,720,315

STABILIZING-TAPERMAKING SYSTEM CLEANER OPERATION Filed Jan. V18, 1971 4 Sheets-Shet 2 FIG. 3

March 13, 1973 R. G. KAISER STABILIZING -'PAPERMAKING SYSTEM CLEANER OPERATION Filed Jan. 18, 1971 4 Sheets-Sheet 3 uwOI m6 QC om ow w QE U E-on Com mmm mmm A Omm 0mm wdl March 13, 1973 R. G. KAISER 3,720,315

STABILIZING "PAPERMAKING SYSTEM CLEANER OPERATION Filed Jan. 18, 1971 4 Sheets-Sheet 4 FIG. 8

3,820,315 STABILIZIN G PAPERMAKING SYSTEM CLEANER OPERATION Robert George Kaiser, Hohokus, N.J., assignor to Clark & Vicario Corporation, North Tarrytown, N.Y. Filed Jan. 18, 1971, Ser. No. 107,157 Int. Cl. B04c 5/18 U.S. Cl. 209-211 18 Claims ABSTRACT OF THE DISCLOSURE Cleaning efliciency in papermaking system cleaners is enhanced by fitting elutriation units on the rejects ends of system cleaners to further dilute cleaner rejects portions and thereby recover more useable fiber in the accepts portion, the dilution being effected by means of a stream of elutriation water admitted to the elutriation unit at relatively low but constant pressure, the accepts and rejects portions from such cleaners being discharged freely into spaces of zones of vacuum of substantially the same condition of vacuum provided by an unobstructed liquid-free core interconnecting such spaces.

BACKGROUND OF THE INVENTION The present invention relates to improvements in papermaking systems and the method and apparatus employed therein for providing stabilized cleaner operation especially when such cleaners are cleaning high consistency stock.

As is well known in the papermaking art, it is desirable that the papermaking stock supplied to the papermaking machine be free of dirt and air in order to produce paper of acceptable quality. Cleaning or de-dirting of the stock conveniently can be accomplished by passing the stock suspension through cleaner units such as hydrocyclones to separate the suspension into a dirt-poor or accepts portion and a dirt-rich or rejects portion. Since the rejects portion discharged from a hydrocyclone commonly contains useable material, e.g., fibers, such rejects portion can be passed through a second cleaning stage to further classify it and thereby enhance the recovery of useable material. Further cleaning stages may be employed to optimize recovery and thus minimize the discharge to waste in a system of useable material. A preferred manner of cleaning a stock suspension in a number of stages and in conjunction with de-aeration of the suspension is described in Kaiser US. Pat. 3,432,036.

It is known that due to poor internal separation of stock within the cleaner, cleaning efiiciency of a hydrocyclone falls when the stock being cleaned therewith has a relatively high consistency, for example, 0.8 or 0.9% or higher. Not only does this result in greater rejection of useable materials but it can cause plugging of the cleaner rejects orifice. Plugged cleaners do not reject, and hence the dirt in the stock discharges through the accepts end of the cleaners and can be delivered as feed to the papermaking machine causing excessive wear in both the cleaners and the papermaking machine. Also, the dirt is carried into the formed paper web and may result in such paper web being rejected as of unacceptable quality. It is desirable therefore that when high consistency stock is being cleaned cleaners fitted with elutriation units be used.

It is also known that the cleaning efficiency of a hydrocyclone cleaner can be increased so that it will reject a higher percentage of dirt with corresponding decrease in the fibers content discharged in the rejects portion by fitting the hydrocyclone at its apex or rejects end with an elutriation device. The elutriation device functions to United States Patent provide a continuation of the cleaner to dilute the rejects fraction with a stream of elutriation water thereby enabling lighter fibers still entrapped in the dirt-rich fraction to separate inwardly from the dirt-rich outer vortex to the upwardly swirling inner vortex of the accepts portion for discharge from the cleaner therewith. While the use of elutriation devices is desirable, employment of such devices in conjunction with hydrocyclone cleaners can present certain problems. For example, where such elutriation devices have been used heretofore in cleaning systems, the cleaners discharging the accepts portion to a positive back pressure and the rejects portion to vacuum or atmosphere have a tendency to plug the rejects end of the cleaner. This plugging is due to the required changes in back pressure, however slight, on accepts because of papermaking head-box requirements, and to the absence of a continuous vacuum core through the longitudinal axis of the cleaner. Also, stability of cleaner operation, i.e., cleaner efiiciency is directly efiected by variation, however slight, in the pressure of the elutriation water feed to the elutriation device. Thus a change in elutriation water pressure or feed for a given condition increases or decreases the reject rate of the hydrocyclone and results in change in rate of rejection of fibers. Furthermore, known methods of installing elutriation devices on cleaners require that relatively high elutriation water pressures of 25 p.s.i.g. or higher be used. High elutriation water pressures can be disadvantageous in that such higher pressures keep dirt orbiting inside the cleaner and attached elutriation device, such orbiting preventing rejection of the dirt and increasing the likelihood of plugging the cleaner. Retention of orbiting dirt Within the cleaner and elutriation device: is undesirable because of the wear it causes to certain components, e.g., the cleaner cone. Further, maintenance of elutriation water feed at relatively high pressures requires expenditure of commensurate levels of power in pumping units.

Finally, it is important that elutriation performance be controlled with exceptional accuracy to avoid creation therewith of conditions which alter cleaner operation stability.

SUMMARY OF THE INVENTION The present invention is concerned generally with improvements in papermaking systems and specifically with improvements in the method and means for providing stabilized hydrocyclone cleaner operation and especially when such cleaners are cleaning stock of a consistency of as high as 0.8% or more.

According to the present invention, cleaning efiiciency of the hydrocyclone cleaners used in various cleaning stages of a papermaking stock cleaning and de-aeration system before ultimate use of the stock in the papermaking machine, can be optimized and stabilized at various feed consistencies by fitting elutriation units to each hydrocyclone cleaner and supplying elutriation Water to the respective elutriation units at relatively low but constant pressure and with equal or uniform distribution to the various elutriation units. The elutriation unit operation is accurately controlled since the operation of the elutriation unit which would alter cleaning efficiency in the hydrocyclone is particularly sensitive to changes in the elutriation water feed as well as back pressure changes acting onthe accepts and rejects discharged from the cleaners.

Further according to the present invention, the elutriation water supplied to the respective elutriation units preferably is lean white Water drawn from the papermaking system, seal pit or save-all, such lean white water being characterized by the absence therefrom of any substantial quantity of fibers.

It is a feature of the present invention that the elutriation units are used on hydrocyclones in systems wherein deaeration of the stock attends the cleaning operation, i.e., accepts from which hydrocyclones have free discharge to a de-aerating zone of vacuum. Moreover, the rejects of such hydrocyclones also have in accordance with the present invention free discharge to a zone of vacuum in a rejects manifold. Preferably, and in accordance with the present invention, the condition of vacuum to which the accepts and rejects portions discharge from the hydrocyclones is delivered is the same, i.e., the degree of vacuum in the respective two zones of discharge is substantially equal and provided by an unobstructed liquid-free core interconnecting the two zones. Such mode of discharge contributes considerably to stabilized cleaning since the discharge of accepts is to a Zone of vacuum and not to a submerged body of accepts or to a conduit. Thus, accepts discharge is free to a constant condition environment wherein no back pressure can act on the hydrocyclone cleaners so that there is no variation which could alter the rejects rate of the cleaner. An alteration in the rejects rate can be of very serious consequences in a papermaking system when cleaning stock of consistencies of as high as 0.8% or more.

A further feature of the present invention is the manner of controlling or stabilizing cleaner operation in systems wherein the stock has relatively high consistency. In supplying elutriation water feed in accordance with the principles of the present invention and in discharging the accepts and rejects portions from such cleaners to a substantially common condition of vacuum, it is possible to effectively clean such high consistency stock without either unduly diluting the stock or permitting plugging of the cleaners to occur. Thus, the present invention is particularly suitable for use in systems making use of high cnsistency stock including those containing high filler contents such as ledger printing, magazine, offset and card stock and particularly those employing fillers to impart electrolytic, magnetic or chemical properties to the finished product. The latter enumerated fillers are relatively expensive, and it is therefore desirable that unnecessary loss of useable quantities thereof be avoided because of poor cleaner efliciency and high rejects rate.

Conservation of rejects is particularly important in that it results in lesser total waste discharge from a cleaning system and contributes to reduction in environmental pollution.

An advantage of the present invention is that it makes possible the use of smaller cleaners when cleaning high consistency stock, since it enables avoidance of plugging of these smaller cleaners under such circumstances while at the same time attaining low rejects rates. Further, it is desirable that such smaller cleaners be used because of their inherently better cleaning efliciency characteristics.

In accordance with the present invention apparatus for controlling and stabilizing the operation of hydrocyclone cleaners in a papermaking system includes an elutriation unit fitted at the rejects end of each hydrocyclone cleaner employed in the system. The hydrocyclone cleaner discharges accepts therefrom directly into a de-aerating zone of vacuum in a free discharge to such zone above the level of any liquid which may be accumulated in the zone. Such de-aeration zone can be the stock receiver providing feed to the papermaking machine or any other receiver suitable for the intended purpose. The rejects end of the elutriation unit also is connected to a zone of vacuum in an unobstructed course to provide free discharge from the elutriation unit.

For the purpose of providing an accurately controlled and constant flow of lean white water as elutriation feed to the elutriation unit, a constant head chamber is provided and receives a supply of lean white water from the source thereof. The lean white water exists as a pond thereof within the constant head chamber, and the constant head chamber is provided with an overflow means for the purpose of maintaining a level of lean white water within the constant head chamber of substantially constant height. A single constant head chamber can be used to supply elutriation feed to all the elutriation units in a particular cleaning stage such as the primary cleaning stage. It also could be used to supply feed to the secondary stage cleaners. Preferably subsequent stages would receive feed from a second separate constant head chamber. A conduit connects the bottom of the constant head chamber with a manifold supplying feed to all of the elutriation units fitted on the hydrocyclones of a given stage in the papermaking system. The constant level of lean white Water therewith esablished and maintained in the constant head chamber thus provides a stabilized flow of elutriation water at a constant head. Lean white water overflowing the overflow means within the constant head chamber is conveyed by means of a conduit connected therewith to the rejects manifold associated with the respective hydrocyclone cleaners. To insure a stabilized level in the constant head chamber and to preclude giving rise to pressure variation in the space above the pond in such constant head chamber, a condition of vacuum can be maintained in the head space of the constant head chamber above the lean white water pond therein by means of a balancing pipe connected with the top of the constant head chamber and the associated hydrocyclone cleaner rejects manifold.

When changes are made in papermaking system operation such as changing grade or furnish to the papermaking machine which changes alter the consistency of stock feed to the hydrocyclone cleaners it is desirable to change the level of head of elutriation feed to control the cleaner rejects rate. This can be accomplished by providing the overflow means, e.g., an overflow pipe in the constant head chamber with a sleeve at the upper portion thereof along with suitable means for adjusting the relative positioning of the sleeve on the overflow pipe. In such apparatus the sleeve is provided with ports which establish the level of lean white Water in the constant head chamber by permitting spill therethrough of the lean White water to the overflow pipe. The adjustment of the height of the level of lean white water in the constant head chamber also can be achieved by employing removably insertable bell fittings on the overflow pipe which fittings serve to effectively lengthen the height of the overflow pipe to specified or required heights.

Further features of the invention provide that regulatory orifice devices can be fitted to the conduit supplying feed to the elutriation units to further optimize such feed delivery such as to compensate for unequal flow from a manifold and therefore have capacity to insure an equalized uniform flow of elutriation feed to all elutriation units.

It also is a feature of the present invention that the elutriation units fitted at the ends of the respective hydrocyclone cleaners can be of the type designed to discharge rejects therefrom in courses other than centrally axially of the unit, e.g., in a tangential outflow rather than axial discharge course as is common in many types of elutriation units while retaining the feature of connecting the free discharge zones to which the accepts and rejects are discharged with an unobstructed liquid free core.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects of the invention will in part be obvious and will in part appear from the following detailed description taken in conjunction with the accompanying drawings, wherein like reference numerals identify like parts throughout, and in which:

FIG. 1 is a schematic representation, with some parts in section and broken away, of improved papermaking apparatus constructed in accordance with the principles of the present invention.

FIG. 2 is an elevational View in section to larger scale, of a portion of the primary cleaning stage of the apparatus shown in FIG. 1, showin the manner in which the elutriation units are connected with the hydrocyclone cleaners of such cleaning stage and the manner of flow of elutriation water to the elutriation unit associated with the respective cleaners which flow is maintained at substantially constant pressure by means of a constant head chamber.

FIG. 3 is an elevational view in section of a modified form of constant head chamber which can be used with the apparatus shown in FIG. 2, characterized by embodiment in the constant head chamber of an adjustable weir for altering selectively the level of constant head of the elutriation water supplied to the elutriation unit therewith.

FIG. 4 is a fragmentary sectional view of a further form of constant head chamber wherein readily removable bell fittings are employed for selectively altering the constant head of elutriation water.

FIG. 5 is an elevational view in section of a portion of a cleaning stage embodying a still further form of constant head chamber in which a notched Weir is provided for selectively altering the head of elutriation water.

FIGS. 6a, b and c are front elevational views of various forms of weirs which can be used in the constant head chamber shown in FIG. 5 and, more particularly, depicting the shapes of notches which can be used in the weirs.

FIG. 7 is a fragmentary view in section showing the use of a regulatory orifice device at the elutriation units associated with the respective cleaner units.

FIG. 8 is a fragmentary sectional view showing an alternative form of elutriation unit wherein outflow therefrom is in a course other than centrally axially of the unit, outflow from the depicted unit being tangentially of the axis of the unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is concerned with improvements in papermakin-g systems and especially the manner and means employing in such systems for providing stabilized cleaner operation maintaining the cleaner efliciency at high rates when cleaning relatively high consistency stock. In the depicted system, a Fourdrinier unit is illustrated as the paper web-forming means. However, it will be understood, that the present invention has applicability to systems having papermaking machines other than the Fourdrinier type, being particularly useful in systems involving papermaking with relatively high consistency stock of as much as 0.8% or more.

Turning now to the system depicted in FIG. 1, it includes a papermaking machine shown generally at 10, to the headbox 12 of which cleaned and deaerated papermaking stock is delivered, and from whence such cleaned and deaerated papermaking stock issues onto the webforming means or wire 14 of the machine. The system also includes a stock receiver 16 which is a hollow structure of suitable size and shape being, by way of example, elongated cylindrical. The stock receiver 16 encloses a chamber 18 which is connected by means of a pipe or conduit 20* with an evacuating means (not shown) for maintaining the chamber 18 under a condition of vacuum suflicient to deaerate paperrnaking stock introduced into such chamber.

The system includes a primary cleaning stage comprised of a plurality of primary cleaner units 22 commonly known in the art as hydrocyclones. A secondary cleaning stage comprised of a plurality of secondary cleaner units 24 also is provided. The primary cleaner units 22 and the secondary cleaner units 24 are arranged to communicate with the interior of stock receiver 16 by means of accepts pipes 26 associated with each of the primary cleaner units 22, and accepts pipes 28 associated with the secondary cleaner units 24. The accepts pipes 26 associated with the primary cleaner units, it will be noted, are disposed within stock receiver 16 at one side of a transverse weir 30 which divides the chamber 18 into a first larger portion and a second smaller chamber 32, the former providing space for accumulating a pond 34 of cleaned and deaerated stock and the latter a space for receiving stock which overflows the weir from pond 34 and as will appear, the accepts discharge from the secondary units 24. The weir 30 serves to maintain pond 34 at an essentially constant level for the purposes described in the Kaiser et al. US. Pat. No. 3,206,917. The accepts pipes 28 of the secondary cleaners on the other hand are disposed in stock receiver 16 at the other side of weir 30, being located in chamber 32.

The primary cleaners 22 preferably are connected in parallel by means of an inlet manifold 36 which delivers an air-containing dirt-rich or uncleaned aqueous suspen sion of papermaking stock to the respective cleaners 22. The aqueous suspension comprises thick stock drawn from system sources such as a stuff box (not shown) or other suitable source thereof and is delivered through conduit 38 along with dilution white water drawn from wire pit 40 through conduit 42 to manifold. 36 by means of pump 44 and conduit 46 connecting manifold 36 with such pump. The aqueous suspension delivered to the primary cleaners also may include the accepts portions of stock cleaned in subsequent cleaning stages and for such purpose conduits 50 and 52 for delivering such subsequent cleaning stage accepts portions are connected with the suction side of pump 44. Alternatively, accepts portions of subsequent cleaning stages can be conveyed directly to the wire pit sump or machine silo.

Connected with the bottom of each primary cleaner 22 is a primary elutriation unit 54, each primary elutriation unit in turn being connected at its lower end to a primary stage rejects manifold 56. Elutriation water feed is provided to each primary elutriation unit 54 through a manifold 58 connected with a constant head chamber 60', the latter being supplied in turn by conduit 62 and pump 64 with lean white water from a suitable source thereof such as a seal pit or save-all, but such source being employed in accordance with the present invention solely for the purpose of providing elutriation Water feed. The construction and function of constant head chamber 60 will be explained in greater detail later on.

The aqueous suspension of uncleaned papermaking stock delivered to the primary cleaners 22 through inlet manifold 36 is separated within the respective cleaners 22 in the manner described, for example, in US. Pat. 2,377,524 into an accepts or dirt-poor portion and a rejects or dirt-rich portion, the accepts portion discharging from the tops of the cleaners 22 through accepts pipes 26 into the evacuated chamber 18 of the stock receiver 16, such discharge being within the free space of the chamber 18 and in manner providing that the de-dirted stock impinges against the receiver structure thereby breaking up and thus facilitating liberation of entrapped goseous media, principally air therefrom. The deaerated and clean primary accepts provide the stock feed to papermaking machine 10, and such stock is withdrawn from the pond 34 through conduit 66 by means of pump 68 for delivery through conduit 70 to the head box 12 of the papermaking machine. The rejects portion in each primary cleaner 22 on the other hand passes downwardly from the cleaner and into the associated elutriation unit 54 wherein further dilution of the rejects portion takes place and further recovery of useable fibers is efiected, such usable fibers being conveyed upwardly in the stream of dilution or elutriation feed to the accepts pipes 26. The rejects or dirt-laden portion then discharges from the respective elutriation units 54 to the primary rejects manifold 56 from whence they are conducted by means of conduit 72 to dilution box 74 for further use in the system as will appear.

Similar to the cleaners 22 in the primary stage, each cleaner 24 in the secondary cleaning stage also is provided with an elutriation unit 76 fitted at the bottom of the respective secondary cleaners 24. Stock feed to the secondary cleaners 24 is provided thereto through secondary inlet manifold 80 from a :source comprised of the primary cleaning stage rejects and dilution white water pooled in dilution box '74 and which is pumped therefrom to the second stage cleaners by means of pump unit 82 through conduit 34 connected to manifold 80. The stock entering the secondary cleaners 24 is separated therein into secondary rejects or dirt-rich portions and cleaned or accepts portions, which discharge through accepts pipes 28 into the free space of chamber 32 in stock receiver 16 wherein such secondary accepts are deaerated in the same manner as described above with respect to the primary cleaning stage accepts. The secondary accepts discharging into chamber 32 as well as the primary accepts overflowing weir 30 are withdrawn from chamber 32 through conduit 50 by means of gravity to the inlet of pump 44 to provide for return to the primary cleaning stage for cleaning therein. The secondary rejects in the secondary cleaners 24 pass into the secondary elutriation units 76 wherein they are further diluted to make possible further recovery of useable fibers and such further recovered fibers along with a portion of the elutriation water exit the cleaners 24 upwardly through the accepts pipes 28 to chamber 32, the heavier particles comprising the secondary rejects and comprised principally of dirt exit from the secondary elutriation units 76 and are collected in secondary rejects manifold 92 from whence they are conveyed by means of conduit 94 to dilution box 96 where such secondary rejects are pooled with dilution white water to provide a source of feed for the cleaners of a third cleaning stage.

The third stage cleaning operation may include use of one or more third stage cleaning units 100, each of which has associated therewith an elutriation unit 102. Pooled stock from the dilution box 96 is conveyed by means of pump 104 and conduit 106 to the third stage cleaner 100 wherein such feed is separated into an accepts and rejects portion in the same manner as earlier described respecting the primary and secondary cleaning stages. The accepts portion is discharged from the cleaner 100 through accepts pipe 110 to the free space 112 of a receiver 114, the latter being connected by means of a pipe or conduit 116 with an evacuating means in the same manner as receiver 16. The third stage accepts collecting in receiver 114 are returned by way of conduit 52 to the suction side of pump 44. The rejects portion from the third stage cleaner 100 are diluted in elutniation unit 102 and further recovery of useable fibers take place, such fibers being discharged into receiver 114. The rejects exiting the elutriation unit 102 are almost entirely dirt, and since they contain little if any useable fibers can be conveyed to a seal box 121 by means of conduit 120 for further possible recovery processing or dicharge to waste.

FIG. 2 illustrates further the aspects of the present invention and more particularly the function and construction of constant head chamber 60 in providing a head of constant pressure of elutriation water to the various elutriation units in the papermaking system. While the depicted arrangement is that associated with the hydrocyclone cleaners 22 of the primary cleaning stage in the system shown in FIG. 1, it will be understood that the ensuing description is applicable to all cleaning stage hydrocyclones. Further, the depiction of the constant head chamber 60 as supplying elutriation water to but one elutriation unit 54 should not be taken as a limitation of the employment of chamber 60. Such single constant head chamber 60 also supplies the remaining primary stage cleaners 22 by means of elutriation feed conduit or manifold 58. It also might 'be employed to supply elutriation water to the secondary stage elutriation units.

Constant head member 60 includes a casing 200, conveniently of cylindrical shape and sized according to elutriation feed water requirements, the casing being a closed structure of air-tight construction for reasons as will appear later. Disposed within casing 200 is an overflow means, i.e., an upright overflow pipe 202, such pipe extending upwardly a substantial distance within casing 200 and having a lower portion thereof extending downwardly from the bottom of casing 200 through a packing gland 204 as shown. The overflow pipe 202 is positioned within the casing 200 such that the upper open end thereof 206 defines and provides an overflow level at which elutriation water 210 present in the constant head chamber will spill over into the overflow pipe. There thus is established Within chamber 60 a constant head supply of elutriation water for delivery to the elutriation unit 54. Conveyance of elutriation water to the elutriation unit 54 is through supply conduit or manifold 58 connected with the bottom of casing 200 as shown, a branch conduit 212 being used to connect each elutriation unit 54 with manifold 58. Supply of elutriation water 210 to chamber 60 as indicated earlier is from a source of lean white water supplied to the casing 200 through conduit 62, although it will be understood that fresh water also could be used. Such supply of lean white water serves to supply only the constant head chamber 60. To insure maintenance of uniform pressure in the conduit or manifold 58 and the branches 212 emanating therefrom when feeding a bank of elutriation units 54, it is desirable according to the present invention to size such conduits so as to provide for a substantially uniform-flow velocity therein.

The head space above the pond 210 of elutriation feed water in chamber 60 is communicated by means of pipe 218 with the interior or rejects manifold 56. In this manner the condition of such headspace is established as one of a condition of vacuum substantially the same as that present in the rejects manifold 56. The condition of vacuum in rejects manifold 56 is also the same stabilized one as that in stock receiver 16 since the liquid-free core in the hydrocyclone and the extension thereof in elutriation unit 154 provides an unimpeded course for establishment of such stabilized condition of vacuum between the respective spaces.

The use of a constant head chamber 60 for supplying elutriation water to the various cleaning stage hydro cyclone elutriation units provides constancy of performance of such units and, in turn, of the hydrocyclone cleaners. By increasing primary stage cleaner efficiency in achieving better dirt separation and recovering more useable fibers, the numbers of subsequent cleaning stages required in a cleaning system and the numbers of cleaners in such stages can be reduced. Furthermore, the method and apparatus of the present invention eliminates the need for making adjustments at individual elutriation units since a bank of the same in a given cleaning stage are all controlled from a single constant head source. This is particularly advantageous in systems where cleaning stages have a large number of cleaners.

Flexibility in elutriation unit operation, as for example, when altering the constant level pressure head in the constant head chamber can be provided with a constant head chamber 220 as shown in FIG. 3. Chamber 220 is similar to chamber 60 and includes a casing 222, an overflow pipe 224, a packing gland 226, vacuum balance pipe 228, conduit 230 for conveying elutriation water spillover to a point of further use such as a rejects manifold, a conduit 232 for delivering lean white water to the chamber, and a conduit 234 for delivering elutriation feed at a constant head pressure to the elutriation units. In contrast with chamber 60, chamber 220 can have the level of elutriation water therein selectively altered, alteration in head pressure being provided by means of an adjustable spillover sleeve 236 slidably received on the upper end of overflow pipe 224. The spillover sleeve is provided with a number of circularly spaced ports 238 through which elutriation water spills over into overflow pipe 224 to thereby establish the constant pressure required. The level is controlled by vertically raising or lowering spillover sleeve 236 by means of a motorized unit 240 from which the spillover sleeve is suspended, a

suitable gland seal being provided at the location of the passage of suspension member 244 through the casing.

FIG. 4 shows a further form of chamber 250 which can be used to provide flexibility for selectively altering the constant pressure of elutriation water supplied therefrom, such chamber including a casing 252 in which is mounted an overflow pipe 254. To vary the effective height of the overflow pipe and hence the constant pressure of elutriation water, one or more bell-shaped fittings 256 can be received on top of the overflow pipe 254 and each other as shown. Such bell-shaped fittings may include means for fastening the same securely against the overflow pipe and each other. For readily removably installing fittings 256 on the overflow pipe, an access plate 258 can be provided at the top of the casing 250 to cover a suitably sized access opening 260.

It will be apparent that various other forms of level control devices can be used for the purpose of establishing and maintaining a constant level of elutriation water in the constant head chamber, such devices not being limited necessarily to spillover pipes. etc.

An advantageous form of constant pressure chamber having capacity for selectively altering the pressure of elutriation water supplied to the various elutriation units without having to excessively alter the water input to the chamber itself is depicted in FIG. 5. Such chamber 300 includes a casing 302 of suitable section and provided with an overflow means of selected character, as for example, in the form of a notched weir 304. The notched weir serves to divide the casing 302 into a constant pressure chamber 308 at one side of the weir, and an overflow chamber 310 at the other side. Lean white water or fresh water is supplied to the constant pressure chamber 308 from a suitable source by means of pump unit 312 and supply conduit 314. The body of liquid in chamber 308 can be controlled selectively at a desired level by controlling the flow of elutriation water delivered by pump 312. Pump 312 will deliver more elutriation water to chamber 308 than is required for operation of the elutriation units receiving feed at a constant pressure from the chamber and through supply manifold 316 connected with the bottom of chamber 308, but such excess will overflow through the weir notch 318 into overflow compartment 310 from which it passes through pipe 320 to a cleaner stage rejects manifold in the manner described earlier. If the constant pressure at which feed is to be supplied to the elutriation units has to be substantially altered, i.e., change the level in chamber 308, this can be achieved easily by a relatively modest alteration in the pumping rate of pump unit 312 inasmuch as the characteristics of a selected weir are utilized to pro vide such change in height of the level with an attendant small change only in weir overflow rate. When making such a change, a sensor device 322 of known type can be used to sense the level in chamber 308 for recordation purposes so that the elutriation water supply from the pump unit 312 can be adjusted responsive to a particular demand.

FIGS. 6a, 6b and 6c show representative forms of weirs which can be used in chamber 300, notched weirs being particularly advantageous for such purpose. Thus, weir 304a of FIG. 6a is one having a ninety degree (90) V-notch therein, while the weir 1504b shown in FIG. 6b is a V-notch type having a notch with an included angle of sixty degrees (60). The flow characteristics of such types of weirs are known for notches of various dimension and, accordingly, it is relatively simple to adapt a particular notch configuration and size to meet system re quirements. FIG. 6c shows a further form of notched weir 3040, that is, one having a dovetail notch 3180.

As has been mentioned before, enhancement of cleaner operation is achieved in accordance with the present invention by fitting system cleaners with elutriation units and by discharging both the cleaner accepts and rejects portions in free discharge to separate zones of vacuum,

the vacuum in the separate zones being substantially equal and being established by an unobstructed liquid-free core extending through each cleaner and associated elutration unit and interconnecting the Zones of free discharge. The presence of such liquid-free core in an unobstructed course interconnecting the spaces at the rejects and accepts discharge ends of the cleaners and associated elutriation units is necessaary if optimum cleaner operation is to be realized. The unobstructed course of the liquid-free core preferably extends longitudinally axially of each cleaner and its associated elutriation unit. With elutriation units of the type depicted in FIGS. 1 and 2, i.e., axial outletting or discharge type, such mode of discharge presents no difliculty respecting existence of an unobstructed axially directed core. On the other hand, known types of elutriation units which employ discharge in a course other than centrally axially of the unit, as for example, those units which have a tangential or radial discharge at the rejects end thereof, are not readily adaptable to permit passage therethrough of a liquid-free core to provide an unobstructed course of such core for interconnecting the zones to which accepts and rejects portions discharge. FIG. 8 depicts one such type unit having a non-axial discharge course, and more particularly a tangentially outletting elutriation device 350 which can be used in a papermaking cleaning system yet be compatible with the presence of an unobstructed liquid-free core passing therethrough. The device 350 is fitted to the lower end of a system cleaner 352, and has a rejects outlet conduit 354 directed tangentially from the unit casing for delivering rejects portions to rejects manifold 356, the unit also being provided with an elutriation feed water inlet line 360 for delivering elutriation water at constant pressure from a feed Water manifold (not shown). In order to maintain the condition of vacuum substantially equal in both the receiver (not shown) to which the cleaner discharges accepts, and the manifold 356 to which the rejects discharge from the elutriation unit 350 by means of unobstructed liquid-free core 362 interconnecting such spaces, the rejects manifold 356 is provided with an upstanding finder pipe 364 extending upwardly from the manifold through the bottom of the elutriation unit as shown. The finder pipe 364 is arranged in axial alignment with both the cleaner and elutriation unit and provides an extension of the liquid-free core 362 through the elutriation unit and into the rejects manifold thereby insuring optimum action of cleaning separation within the elutriation unit by reason of maintenance of the liquid-free core therein notwithstanding the tangential discharge course of the rejects exiting therefrom. In addition to providing a core extension path, finder pipe 364 can in the event of plugging of outlet conduit 354 serve as an outlet conduit for conveying rejects to manifold 356 thereby to preclude discharge of dirt-rich stock out of the accepts ends of cleaner 352.

By providing elutriation water feed from a constant head chamber, e.g., chamber 60 shown in FIG. 2, so that such water feed is at constant pressure to the various elutriation units 54, such feature along with free discharge of both accepts and rejects portions to zones of vacuum, system cleaner operation is readily and optimally controlled to insure high cleaner efliciency and avoidance of cleaner plugging. As was noted earlier, elutriation water feed preferably is through manifold 58 which in turn is connected with individual branch supply lines 212 connected with the respective elutriation units. While constant head chamber 60 functions to provide elutriation water feed to all elutriation units 54 at constant pressure with such pressures being the same in all branch lines 212, it is advantageous to provide each of such branch lines 212 with a regulator unit 400 as shown in FIG. 7. Each regulator unit 400 functions to provide an equalized flow rate to each of the elutriation units 54 to insure against 'any flow rate variations which may exist in any of the various branch lines 212 being supplied from the same manifold 58.-

The foregoing description illustrates methods and apparatus by which the advantages of this invention can be attained, but these descriptions are merely illustrative and should not be construed as limiting since modifications thereof will be readily apparent to those skilled in the art. For example, it is not necessary that each elutriation unit 54 be provided with a regulator unit 400 since in cleaning stages with only a few cleaners equalized flow rate may not be a problem in the various branch lines 212. Other modifications could include the employment of a bafile 440 in the stock receiver 16 to preclude co-mingling of the first stage cleaner accepts with the second stage cleaner accepts in that vessel. It will be apparent too that other modifications in the system could include returning third stage cleaner accepts to the second stage cleaner feed by way of dilution box 74 in known manner. Furthermore, the third stage cleaner units 100 could be fitted to discharge directly to the compartment 32 in stock receiver 16 instead of providing a separate vessel as shown in FIG. 1.

From the foregoing description it will be discerned that the present invention provides a particularly advantageous method and apparatus for enhancing the operation of cleaning stage cleaners in papermaking systems. To achieve the salutary results provided by the present invention, it is essential that both the accepts and rejects portions be discharged in free discharge to zones of vacuum and that the vacuum in the zones of discharge be substantially equal and that they be provided by a common means, namely, a liquid-free core extending through the cleaner and attached elutriation unit, which interconnects the two zones. Such features coupled with the utilization of an elutriation water feed of constant pressure to the respective elutriation units not only optimizes cleaner efl'iciency but measurably reduces the potential for clogging of cleaner units.

What is claimed is:

1. A method for improving and stabilizing cleaning efiiciency of a hydrocyclone cleaner operating in a papermaking system to clean papermaking stock by separating it into a dirt-poor accepts portion and a dirt-rich rejects portion which comprises receiving the rejects portion from the cleaner in an elutriation unit fitted to said cleaner,

diluting the rejects portion from said cleaner received in said elutriation unit with elutriation water drawn from a constant pressure source thereof thereby to uniformly control the rejects rate and the u'seable stock present in the accepts portion,

conveying both the accepts portion in said cleaner and the rejects portion in said elutriation unit to separate zones of vacuum, and

establishing a common condition of vacuum in each of said separate zones by interconnecting said zones with an unobstructed liquid-free core passing completely through said cleaner and elutriation unit.

2. The method of claim 1 wherein the constant pressure source of elutriation water is drawn from a source of lean white water in the papermaking system.

3. The method of claim 1 wherein the constant pressure source of elutriation water is drawn from a source of fresh water in the papermaking system.

4. The method of claim 1 wherein the elutriation unit is attached to the rejects end of said cleaner and said liquid-free core extends axially of said cleaner and said elutriation unit.

5. The method of claim 4 wherein the rejects portion discharges from said elutriation unit co-axially with said liquid-free core.

6. The method of claim 4 wherein the rejects portion discharges from said elutriation unit at locations radially spaced from said liquid-free core.

7. The method of claim 6 wherein discharge at said locations is in a course substantially parallel with said liquid-free core.

8. The method of claim 4 wherein the rejects portion discharges from said elutriation unit in a course substantially tangentially of said liquid-free core.

9. In apparatus for cleaning and deaerating an aqueous suspension of papermaking stock which includes a centrifugal cleaner for separating suspension into dirt-rich and dirt-poor fractions,

means for supplying suspension to said cleaner with sufiicient force to separate it therein into said dirtrich and dirt-poor portions and to discharge said portions from said cleaner, said cleaner having separate outlets through which said dirt-rich and dirtpoor portions discharge therefrom,

an enclosed receiver adapted to receive the dirt-poor portion from the cleaner and collect it as a pond therewithin,

evacuating means connected to the receiver for maintaining the interior thereof under vacuum,

pipe means connecting the dirt-poor discharge outlet of said cleaner with said receiver, said pipe means terminating in an open end within said receiver above the level of any pond of suspension collecting therein for conveying said dirt-poor portion to the evacuated space within said receiver,

an elutriation unit connected with said cleaner and having an elutriation chamber communicating in air-excluding relationship with the dirt-rich discharge outlet of said cleaner, said elutriation unit having a discharge outlet,

a manifold for collecting dirt-rich stock in communication with the discharge outlet of said elutriation unit,

a source of elutriation water,

means for connecting said elutriation unit with said source and for admitting said elutriation water to said unit, and

means for maintaining constant the pressure at which said elutriation water is supplied to said elutriation unit, said pipe means, said cleaner and said elutriation unit being disposed in coaxial alignment to provide an unobstructed course for a liquid-free core extending through said pipe means, cleaner and elutriation unit interconnecting the evacuated space of said receiver and the interior of said manifold.

10. The apparatus for claim 9 wherein the means for maintaining constant the pressure of the elutriation water feed to said elutriation unit comprises a constant head chamber including a casing, a conduit for admitting a flow of elutriation water to said casing, overflow means disposed in said casing for establishing a pond of elutriation water of constant level within said casing, and conduit means for conveying liquid overflowing said overflow means to said manifold, and a pipe connecting a lower part of the pond in said casing with said elutriation unit.

11. The apparatus of claim 10 comprising a plurality of centrifugal cleaners, and a separate elutriation unit connected with each cleaner, at least some of said cleaners being connected with a common constant head chamher by means of branch lines receiving elutriation water from said constant head chamber, and a regulator unit in each branch line for providing equalized flow rate of elutriation water to the respective elutriation units connected with said common constant head chamber.

12. The apparatus of claim 9 wherein means are provided for selectively altering the height of said overflow means to thereby selectively vary the level of elutriation water in the pond in said casing and the pressure at which elutriation liquid is supplied to said elutriation unit.

13. The apparatus of claim 12 wherein said overflow means comprises an upright pipe disposed in said casing, the interior of said pipe communicating with the overflow conduit means, a tubular sleeve closely encircling the upper end of said upright pipe, and means for vertically adjusting the positioning of said sleeve on said upright pipe to correspondingly vary the level at which water over flows the elutriation water pond into said upright pipe.

14. The apparatus of claim 12 wherein said overflow means comprises an upright pipe disposed in said casing, the interior of said pipe communicating with the overflow conduit means, and at least one fitting removahly connectable with the upper end of said upright pipe for increasing the height thereof and correspondingly, the level at which water overflows the elutriation Water pond into said upright pipe.

15. The apparatus of claim 12 wherein said overflow means comprises a weir.

16. The apparatus of claim 15 wherein said weir is a notched weir for providing relatively substantial change in the height of said elutriation pond with relatively small change in the rate of overflow of said notched weir.

17. The apparatus of claim 9 wherein said elutriation unit is disposed to discharge dirt-rich stock axially therefrom to said manifold.

18. The apparatus of claim 9 wherein said elutriation References Cited UNITED STATES PATENTS 3,331,193 7/1967 WOOdl'lliT 55-19l 3,347,372 10/1967 BouchiilOn 209-2l1 3,415,375 12/1968 Wikdahl 209211 3,421,622 l/1969' Wurtmann 554l X 3,432,036 3/1969 Kaiser 209-211 FRANK W. LUTTER, Primary Examiner R. J. HILL, Assistant Examiner UNITED STATES PATENT OFFICE QERTIFICATE @F CQRRECTION Paoent my 3,720,315 Dated March 13, 1973 Inventoflsg) Robert G. Kaiser It is certified that error appears in the above-identified patent and that sz id Letters Patent are hereby corrected as shown below:

Column 1, line 1, "3,820,315" should read --3,72o,315--.

Column 6, line 53, 'goseous" should read 7 -gase0us-=-.

Column 7, line '70, "r nem'ber shcm lci read --chamber-:. I

Signed and sealed this lth day of April 1971 (SEAL) Attest:

EDWAl'iD H FILER/HER, JR G PIAiQSEiAI-JL DANN Atto sting Officer Commissioner of Patents FORM PC4050 (10-69) USGO'MM-DC 80376-P69 I: v.8. anvlmmur nmmm: emu: an o-ucuu 

